Apple's announcement of iOS 4 and the iPhone 4 in just the last three months shows that the smartphone wars aren't cooling yet. Just consider everything that has happened in the space of the last year. Microsoft's Windows Phone 7 is a top-to-bottom overhaul of the Windows Mobile OS, and Google continues to aggressively roll out updates to Android. Palm hasn't been quite as active in the news recently, but we're not discounting its WebOS quite yet.

The following chart compares popular features from the smartphone operating system that have been most active this year. Note that we left RIM off because the manufacturer has not issued major updates in the past 12 months. A quick look at the chart demonstrates just how competitive the OS battle has become. As each company fires a shot, you can expect its competitors to respond in force. And that's something we love to watch.

Yes, but limited. Third-party apps will not be allowed to run in the background.

Notifications

Yes, but only one at a time

Yes, with multiple notifications bar

Yes

Yes

App folders

Yes

Yes

No

Apps arranged in "Hubs"

Tethering

Yes

Yes, with built-in support for tethering and mobile hotspot feature

Yes, but dependent on carrier

TBD*

VoIP

Yes, with third-party apps

Yes, with third-party apps

Yes, with third-party apps

TBD

Gaming

Many gaming apps available. Game Center feature adds new functionality

Many gaming apps available

Palm publicly released its PDK in March for game development. 3D games are already available.

Xbox Live integration

Flash support

You're kidding, right?

Yes

Yes

Yes, but not at launch

Number of titles in App Store

iTunes App Store: More than 225,000

Android Market: More than 30,000

Palm App Catalog; More than 2,400

Windows Phone Marketplace; hasn't launched yet

Voice commands

Yes

Yes

No

TBD

Mass storage

No

Yes

Yes

TBD

Universal search

Yes

Yes

Yes

Yes

Music store

iTunes Music Store

Amazon MP3 Store

Amazon MP3 Store

Zune

Web browser

Safari

Android

WebKit

Internet Explorer

Copy-paste

Yes

Yes

Yes

No

Pinch and zoom multitouch

Yes

Yes

Yes

Yes

Video calling

Yes, but iPhone 4 only

Yes, but on limited phones

No

Not yet

* Microsoft has yet to fully detail the features for Windows Phone 7.Editors' note, Monday, April 12, 2010: This chart was updated to show that Palm WebOS 1.4 supports third-party VoIP applications. This chart was further updated on June 14, 2010, to reflect the changes from iPhone 4 and Android 2.2